| Name | Children | Media (from resource) | Traits |
|---|---|---|---|
| Collotheca | 1 | 0 | 0 |
| Collothecidae | 1 | 0 | 0 |
| Cosmarium Corda ex Ralfs 1848 (cosmarian algae) | 1 | 0 | 0 |
| Cribraria Persoon ex Roemer 1794 | 1 | 0 | 0 |
| Cribrariaceae | 1 | 0 | 0 |
| Cromulinaceae | 1 | 0 | 0 |
| Cryptomonadaceae | 2 | 0 | 0 |
| Cryptomonas Ehrenberg 1831 | 1 | 0 | 0 |
| Cyclidiidae | 1 | 0 | 0 |
| Cyclidium O. F. Müller 1773 | 1 | 0 | 0 |
| Desmidiaceae | 3 | 0 | 0 |
| Diachea leucopodia | 1 | 0 | 0 |
| Dictyosphaerium Nägeli 1849 | 1 | 0 | 0 |
| Didymiaceae | 1 | 0 | 0 |
| Difflugia Leclerc 1815 | 2 | 0 | 0 |
